1. Field of the Invention
The present invention relates to a hydraulic working machine such as a hydraulic excavator.
2. Description of the Related Art
Hydraulic excavators including a revolving upper structure rotatably mounted on a mobile lower structure or undercarriage and a driver's cab provided on the revolving upper structure are known in the art. It is also generally known that an internal combustion engine serving as a power source for a hydraulic motors is disposed in a rear portion of the revolving upper structure.
In the hydraulic working machine of the type described above, a directional control valve is mounted in the revolving upper structure for actuating various hydraulic cylinders, such as a boom hydraulic cylinder, and a swing hydraulic motor according to manipulation of control levers at the cab. A hydraulic oil tank and a fuel tank for the internal combustion engine are also mounted in the revolving upper structure. Conventionally, the directional control valve is disposed beneath the cab in which the control levers are provided.
The directional control valve while in operation generates heat and operation noise. According to the conventional arrangement, since the directional control valve is disposed beneath the cab, the heat and operation noise from the directional control valve are directly transmitted to the cab, posing severe discomforts on an operator. In addition, since the directional control valve is provided with a plurality of pipelines connected to the hydraulic cylinders and the swing hydraulic motor, the maintenance of the directional control valve ad the pipelines should necessarily involve a tedious and time-consuming cab-removing work.
Furthermore, the position of the directional control valve and the pipelines is important as it may increase the length of the pipelines extending from the directional control valve, which will bring increases in cost and hydraulic pressure loss. The directional control valve when arranged at a position susceptible to an external shock impact is likely to be damaged.